Trousers, such as jeans, have belt loops that are stitched onto the waistband at predetermined intervals. The loops are stitched either manually or automatically depending on the manufacturing plant and machinery setup.
In manual belt loop stitching, an operator advances the waistband by hand through a stitching station of a sewing machine, places a belt loop over the waistband, and stitches the belt loop. This type of belt loop stitching is expensive, time-consuming and labor intensive. An automated belt loop stitching setup therefore has become more desirable.
In one automated system, indicia marks corresponding to the desired belt loop positions are placed on the waistband. The stitching machinery senses the marks by appropriate sensing systems and automatically stitches the belt loops onto the waistbands where a mark has been sensed. This system requires an extra step, i.e., marking the waistband, thus raising production and other attendant costs.
In the automated belt loop stitching operation disclosed in U.S. Pat. No. 4,555,999 to Conner, marks are not placed on the waistband, thus overcoming the marking drawback of the prior system. In Conner, the operator places the waistband at the stitching station beginning at the rear seam, and then stitches a belt loop. The machine automatically indexes the waistband counterclockwise to the end while counting the distance with a stepper motor control unit. The machine then reverses machine direction and indexes to the correct loop positions while stopping waistband movement intermittently for belt loop stitching based on the measured distance of the entire waistband.
Although the Conner apparatus automates belt loop attachment, it has some drawbacks because 1) the indexed positions must be calculated symmetrically from the rear seam, and 2) the trousers must be reversibly moved through the apparatus, first in one direction, followed by movement in the reverse direction.
It would be more desirable to use known reference points which are formed integral to the trousers for correlating the belt loop positions on the waistband. Such reference points would desirably include the waistband seams. Because the seams are formed integral with the trousers, there is no need to apply separate indicia as noted above. Because belt loop attachment positions are correlated with known reference points such as seams it would not be necessary to calculate distance based on the time consuming, reversing movement such as disclosed in Conner.
During production, known variables such as the detected position of a seam and the required number of belt loops would be correlated. As the waistband moves through a stitching station, belt loops could be stitched at intermittent intervals without requiring complex waistband measurements such as the reversible waistband movement disclosed in Conner. Additionally, any detection means would preferably be simple, using electromechanical apparatus that register the bulge of a seam or other integrally formed structure rather than complex electronic sensing apparatus such as in Conner.